Greenhouse shade cloth

[swamprad]

My new 18 x 24 greenhouse is all framed up, and will soon be finished! I'll post a thread with photos when we finish. But I need some help figuring out how to make the shade cloth work for me.

My new greenhouse is triple polycarbonate, which already blocks 20% of the light. I am going to use the aluminet shade cloth, but I'm not sure what percentage I need. My collection is probably 3/4 slippers, but I have quite a few catts, oncidiums, and other high light plants, not to mention the phrags and multifloral paphs, which are also high light.

The first question is what percentage shade cloth do I need for low light slippers, and what percentage shade cloth do I need for catts and other high light genera?

The second question is, how do I manage to satisfy the light requirements of both low light and high light plants in the same greenhouse?

Some people have told me to hang the high light plants up high and keep the lower light plants underneath, which seems sketchy to me at best. i.e., unless you had a fairly uniform number of hanging plants blocking light, you'd have a mixture of too sunny areas and too shady areas on the bench.

Or, should I have two "strengths" of shade cloth, one for each end of my greenhouse, to create a high light area and a low light area? This doesn't seem like a good idea either, since the sun moves back and forth in the sky, and doesn't shine down from directly above. Light may shine through the high light shade cloth on a slant and burn my low light slippers, even though they are directly below the low light shadecloth.

Or, should I have a moderate shade cloth on the outside of the entire house, which would be suitable for the higher light plants, and then rig up a second shade cloth inside the house a few feet above my low light slippers? Actually, this seems like it may be the more logical option.

I'd appreciate any and all comments! How have you guys solved this problem?

 

[Candace]

Mark, if "looks" aren't a big issue, you can always put on shading paint on the outside(underneath the shade cloth) on the part of the g.h. you'll have your slippers. I bought some especially made for g.h.'s so that it's not permanent. And you can add more coats to get the coverage/light that you need. It usually lasts a few seasons until you have to touch it up.

 

[emydura]

I prefer shadecloth over paint or shaded polycarbonate etc. Mainly because I think it is better at reducing heat buildup in the glasshouse (I come from a climate of very hot bright summers). Some people here have polycarbonate houses without shade cloth and they heat up like an oven on a hot summers day. Mine never gets above 30oC. Plus the other advantage of shade cloth is that you can easily slip on or off extra layers as need be (which I do a couple of times a year).

For my multis I have one layer of 70% (sandstone colour) during winter and 2 layers of 70% during summer. This sounds excessive but they seem to be getting too much light if anything.

I grow my shaded paphs as your last suggestion. Under an extra layer of shade cloth (70%) within the glasshouse. Seems to work OK. Maybe a little too much shade.

David

 

[orcoholic]

What % of shadecloth you need depends heavily on where you live and how your greenhouses are oriented.

I think you could get a good idea from talking to local nurseries. A light meter that measures footcandles is also very helpful. The amount of fc that each orchid likes is readily available.

Having said that, in Memphis, south of Phila where I grow, I would think that during the winter you could get away with little or no shading for the bright plants, since you are already getting 20%, and an additional 20-30% for the low light plants. I use no shading for the bright plants (Catts and multis) and 30% for Phals. The greenhouses stay like this from the beginning of Nov - end of Feb.

At the end of Feb I put a 40% cloth on and keep it that way until Nov.

You will also be able to take advantage of the orientation of the greenhouse to the sun. During the midwinter, the sun stays low in the sky and shines in one side of the greenhouse. My bright light plants are on that side. During the summer (6/21) the light is consistent all day and passes right over the center of the house.

When calculating how much shade you are actually buying you need to realize two 40% shade cloths do not provide 80% shade. The first layer shades 40% which leaves 60% of the light available for the plants. The second layer shades 40% of the remaining 60%, or 24%. So two 40%s = 64% total shade (or something right around that).

Mike

 

[cnycharles]

if you can move your curtain using motors (open, close) then you could use several pieces of curtain instead of one whole piece (inside, if you have space to allow the curtain to go across the whole roof area. that way, you close the curtain a little and it shuts out say 10% of the sun coming in (not counting the percentage shade the aluminet makes). you could calculate how much shade you would need on your brightest day for your shadiest plants, and then only close the curtain a little or a lot depending on how hot or bright it is. one end of a piece of curtain is hooked to a standard profile (doesn't move) and the other to a moving one. pushbars hooked to gears hooked to motor drivebar moves all the profiles at the same time. I think you could do something like this with an outer shadecloth if your roof didn't have anything to catch it moving on and it was small enough that you could drag it back and forth by hand, and you could guarantee a way to tie it down so that the wind didn't catch it. inside you would use plastic or wire curtain strings to hold the curtain up, and some on top to prevent wind from pulling it up. I think something could be rigged for a small house, but I would never be able to explain it without too many words! (my fault in lack of good explanation)

I agree that it seems better to reflect the light than to use dark cloth or paint to catch the light. we have some houses at work that are blackcloth for controlling daylength, and those houses can get unbearably hot. other houses have reflective media (not suitable for controlling daylength) and are a lot cooler. other newer large ranges have reflective media on top of curtain, and black mesh underneath. it's heavy and bulky, but is the coolest. obviously it has total shading or nearly so, so if closing to control heat then you have no light, and too much contrast in the spots with light and dark

 

[goldenrose]

I use several of the above methods. I have aluminet, I've had it for years, I think it's 50%. My GH runs N/S, there are maples on the west that shade it starting around 2, the aluminet covers the peak & the east side & is down from 9:30/10-1:30/2. The higher light plants are at the south end, the med-lower light at the north end. The lower shelf has what I think were lower light/shade plants but I supplemented some with 4' flourescent the past 6 weeks & they've responded nicely.